Note 254 — Chapter XVI · More Difficulties and more Inventions—Boulton again in Cornwall.

The above illustration represents the first engine employed at Soho, with the alterations subsequently introduced, for the purpose of producing rotary motion. The old Kinneil engine, “Beelzebub,” as Watt called her, was entirely removed, and replaced by this engine, as explained by Watt in his MS. Memoir of Boulton now before us, wherein he states,—“The first engine of 18 inches cylinder, which was employed in returning the water to Soho mill, was replaced about 1778 or 1779 by a larger engine, the first on the expansive principle, which still remains there.” The engine became known at Soho as “Old Bess,” and she continued in regular work until within the last eight years. The illustration shows the state in which the engine now stands in South Kensington Museum.

A. steam cylinder; B. steam pipe; C. throttle valve; D. steam valve; E. eduction valve; F. eduction pipe; G. valve gearing; H. condenser; I. air pump; K. air pump rod; L. foot valve; M. hand gear tappet rod; N. parallel motion; O. balance weight; P. rocking beam; Q. connecting rod; R. feed pump rod; S. sun wheel; T. planet wheel; U. fly wheel; W. governor; X. feedwater cistern.